This invention relates generally to circuits that are switchable or reconfigurable using MEMS (microelectromechanical systems) technology and, more particularly, to tunable impedance matching circuits using MEMS switches. In general, there are various types of electrical circuits for which reconfiguration is desired to maintain functionality or efficiency. MEMS switches, the states of which can be changed by the application of electrical signals, have often been proposed for use in highly reconfigurable circuits. Unfortunately, although MEMS components have negligible insertion loss in comparison with electronic switches, such as field-effect transistors (FETs), MEMS switches tend to be less reliable because their movable metal components are inherently subject to metal fatigue. In addition, when MEMS switches are called on to handle high power input, they are typically subject to “sticktion,” i.e., to fusing in one switch position. A high electromagnetic field across the MEMS switch contacts induces arcing. There is, therefore, an inherent upper power limit for MEMS switches, above which the switches fuse in their current positions.
An important need for circuit reconfiguration arises in impedance matching of electronic components. Mismatched components, particularly those operating at radio frequencies (RF), are inefficiently coupled and the mismatch gives rise to a voltage standing wave in each component. The degree of mismatch may be expressed in terms of the voltage standing wave ratio (VSWR). This phenomenon is a key system performance degradation mechanism in many electronic systems, especially those operating at high frequencies. The phenomenon is often difficult to resolve and predict. Solutions employed prior to the present invention include placement of discrete high-value attenuators in a signal transmission path, or manually tuning the transmission path to minimize the adverse effect of the mismatch. These techniques are, however, undesirable because they are both costly and labor intensive to implement in a high-volume manufacturing environment. Accordingly, there is still a need for a technique for reconfiguring circuits, such as matching circuits, using MEMS devices, but without the disadvantages usually associated with them. The present invention satisfies this need.